/*
 * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.awt.geom;

import java.util.*;

/**
 * A utility class to iterate over the path segments of an ellipse
 * through the PathIterator interface.
 *
 * @author Jim Graham
 */
class EllipseIterator implements PathIterator {

  double x, y, w, h;
  AffineTransform affine;
  int index;

  EllipseIterator(Ellipse2D e, AffineTransform at) {
    this.x = e.getX();
    this.y = e.getY();
    this.w = e.getWidth();
    this.h = e.getHeight();
    this.affine = at;
    if (w < 0 || h < 0) {
      index = 6;
    }
  }

  /**
   * Return the winding rule for determining the insideness of the
   * path.
   *
   * @see #WIND_EVEN_ODD
   * @see #WIND_NON_ZERO
   */
  public int getWindingRule() {
    return WIND_NON_ZERO;
  }

  /**
   * Tests if there are more points to read.
   *
   * @return true if there are more points to read
   */
  public boolean isDone() {
    return index > 5;
  }

  /**
   * Moves the iterator to the next segment of the path forwards
   * along the primary direction of traversal as long as there are
   * more points in that direction.
   */
  public void next() {
    index++;
  }

  // ArcIterator.btan(Math.PI/2)
  public static final double CtrlVal = 0.5522847498307933;

  /*
   * ctrlpts contains the control points for a set of 4 cubic
   * bezier curves that approximate a circle of radius 0.5
   * centered at 0.5, 0.5
   */
  private static final double pcv = 0.5 + CtrlVal * 0.5;
  private static final double ncv = 0.5 - CtrlVal * 0.5;
  private static double ctrlpts[][] = {
      {1.0, pcv, pcv, 1.0, 0.5, 1.0},
      {ncv, 1.0, 0.0, pcv, 0.0, 0.5},
      {0.0, ncv, ncv, 0.0, 0.5, 0.0},
      {pcv, 0.0, 1.0, ncv, 1.0, 0.5}
  };

  /**
   * Returns the coordinates and type of the current path segment in
   * the iteration.
   * The return value is the path segment type:
   * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
   * A float array of length 6 must be passed in and may be used to
   * store the coordinates of the point(s).
   * Each point is stored as a pair of float x,y coordinates.
   * SEG_MOVETO and SEG_LINETO types will return one point,
   * SEG_QUADTO will return two points,
   * SEG_CUBICTO will return 3 points
   * and SEG_CLOSE will not return any points.
   *
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  public int currentSegment(float[] coords) {
    if (isDone()) {
      throw new NoSuchElementException("ellipse iterator out of bounds");
    }
    if (index == 5) {
      return SEG_CLOSE;
    }
    if (index == 0) {
      double ctrls[] = ctrlpts[3];
      coords[0] = (float) (x + ctrls[4] * w);
      coords[1] = (float) (y + ctrls[5] * h);
      if (affine != null) {
        affine.transform(coords, 0, coords, 0, 1);
      }
      return SEG_MOVETO;
    }
    double ctrls[] = ctrlpts[index - 1];
    coords[0] = (float) (x + ctrls[0] * w);
    coords[1] = (float) (y + ctrls[1] * h);
    coords[2] = (float) (x + ctrls[2] * w);
    coords[3] = (float) (y + ctrls[3] * h);
    coords[4] = (float) (x + ctrls[4] * w);
    coords[5] = (float) (y + ctrls[5] * h);
    if (affine != null) {
      affine.transform(coords, 0, coords, 0, 3);
    }
    return SEG_CUBICTO;
  }

  /**
   * Returns the coordinates and type of the current path segment in
   * the iteration.
   * The return value is the path segment type:
   * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
   * A double array of length 6 must be passed in and may be used to
   * store the coordinates of the point(s).
   * Each point is stored as a pair of double x,y coordinates.
   * SEG_MOVETO and SEG_LINETO types will return one point,
   * SEG_QUADTO will return two points,
   * SEG_CUBICTO will return 3 points
   * and SEG_CLOSE will not return any points.
   *
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  public int currentSegment(double[] coords) {
    if (isDone()) {
      throw new NoSuchElementException("ellipse iterator out of bounds");
    }
    if (index == 5) {
      return SEG_CLOSE;
    }
    if (index == 0) {
      double ctrls[] = ctrlpts[3];
      coords[0] = x + ctrls[4] * w;
      coords[1] = y + ctrls[5] * h;
      if (affine != null) {
        affine.transform(coords, 0, coords, 0, 1);
      }
      return SEG_MOVETO;
    }
    double ctrls[] = ctrlpts[index - 1];
    coords[0] = x + ctrls[0] * w;
    coords[1] = y + ctrls[1] * h;
    coords[2] = x + ctrls[2] * w;
    coords[3] = y + ctrls[3] * h;
    coords[4] = x + ctrls[4] * w;
    coords[5] = y + ctrls[5] * h;
    if (affine != null) {
      affine.transform(coords, 0, coords, 0, 3);
    }
    return SEG_CUBICTO;
  }
}
